PROJECTS

The CalCOFI marine mammal monitoring program examines seasonal and inter-annual patterns in density, abundance, and distribution on a longer continuous time scale and with a higher rate of sampling than previous cetacean surveys off the California coast, particularly for the winter and spring periods, for which there are currently few data available.

The goal of our project “Southern California Beaked Whale Occurrence from Towed Array Surveys” is to support the US Navy environmental compliance requirements for monitoring marine mammals. This research effort is performed by the University of California San Diego (UCSD) Scripps Institution of Oceanography (SIO) in La Jolla, CA as part of a larger effort. Data collected by a shipboard towed array acoustic survey for marine mammals is being analyzed. These data will provide for spatial assessment of Southern California beaked whale occurrence from towed array surveys.

Marine mammal surveys, initiated as part of the CalCOFI cruises in 2004, were continued during 2016-2017. Visual monitoring incorporated standard line-transect survey protocol which includes two experienced observers scanning for marine mammals during transits between CalCOFI stations.

Cetacean distribution, density and abundance in the Southern California Bight were assessed through visual and acoustic surveys during eighteen California Cooperative Oceanic Fisheries Investigations (CalCOFI) cruises from February 2012-April 2016. Visual monitoring incorporated standard line-transect protocol during all daylight transits while acoustic monitoring employed a towed hydrophone array during transits and sonobuoys deployed at oceanographic sampling stations. Visual effort included 2,031 observation hours covering 31,807 kilometers. A total of 1,914 sightings were made, which included 18 different cetacean species. Acoustic effort included 1m027 sonobuoy deployments and 478 towed array deployments.

A Distance based visual line-transect survey was designed to gather baseline data on the occurrence, distribution, and population estimations of marine mammals near Silver Strand Training Complex (SSTC) and San Diego Bay (SDB). During the warm and cool season periods between October 2013 and September 2014, seventeen survey days were completed (890.8 km) in SSTC and north San Diego Bay (NSDB). During the course of these efforts, 280 observations were made in the survey areas. Six marine mammal species were sighted, with the predominant species being California sea lions (Zalophus californianus [SSTC, n=132] and NSDB, n=109). Odontocete observations (n=26) were largely comprised of Tursiops truncatus and Delphinus spp. Mysticete whales (Eschrichtius robustus) were sighted in nearshore shallow waters of SSTC during January, February, and April–June.

The present study provides new and current estimates of cetacean density for the six most commonly encountered cetacean species off southern California based on sighting data collected during 37 quarterly CalCOFI cruises from 2004 to 2013. The current study resulted from a high survey repetition rate that allowed for the examination of inter-annual and seasonal trends in density as well as temporal and spatial patterns of distribution for six common cetacean species off southern California: blue whales, fin whales, humpback whales, short-beaked common dolphins, Pacific white-sided dolphins, and Dall’s porpoise.

Cetacean distribution, density and abundance in the Southern California Bight were assessed through visual and acoustic surveys during five California Cooperative Oceanic Fisheries Investigations (CalCOFI) cruises from August 2012-November 2013. Visual monitoring incorporated standard line-transect protocol during all daylight transits while acoustic monitoring employed a towed hydrophone array during transits and sonobuoys at oceanographic sampling stations. Visual effort included 584 observation hours covering 10,900 kilometers yielding 565 sightings of 15 identified cetacean species.

Documenting year-round diversity and distribution of marine mammals off Southern California is important for assessment of effects of potentially harmful anthropogenic activities. Although the waters off Southern California have been surveyed extensively for marine mammals over the past 18 years, such surveys have been periodic and were conducted primarily from summer to fall, thereby missing potential seasonal shifts. We examined seasonal abundance and population density of cetaceans off Southern California from 16 shipboard line-transect surveys conducted quarterly during 2004–08. The study area consisted of 238,494 km² of coastal, shelf, and pelagic oceanic habitat from near-shore waters to 700 km offshore.

Spatial and temporal distribution patterns, density and abundance of cetaceans in the southern California Bight were assessed through visual and acoustic surveys during five California Cooperative Oceanic Fisheries Investigations (CalCOFI) cruises from August 2011 – July 2012. Visual monitoring incorporated standard line-transect protocol during all daylight transits while acoustic monitoring employed a towed hydrophone array during transits and sonobuoys at oceanographic sampling stations.